1. Technical Field
The present invention relates to an ink composition for ink jet recording and an ink jet recording method.
2. Related Art
Some known printing methods are based on ink jet recording, a technique by which images can be recorded on a recording medium by discharging fine droplets of ink from nozzles of a recording head onto the recording medium. The ink jet recording technology has greatly advanced in recent years, and such printing methods using ink jet recording are now also used in the area of high-definition image recording, previously possible only by photography or offset printing. Various proposals have been made about inks for this purpose, in particular, inks with which high-quality images can be recorded on recording media that absorb little or no ink.
Images recorded on a recording medium that absorbs little or no ink do not firmly adhere to the recording medium in some cases. An example of a way to make such images more firmly fixed is to add a resin emulsion (a fixing resin) to the ink. More recently, core-shell resin emulsions have been used to add various functions to inks while improving the fixation of images.
For example, JP-A-2002-12802 discloses the use of a core-shell particle that has a core portion made of a thermoplastic resin and a shell portion made of a three-dimensionally crosslinked resin so that recorded images can be stored well and can be erased from the recording medium as necessary for repeated use of the recording medium. JP-A-2012-25947 discloses the use of a core-shell particle that has a core portion made of an acrylic resin and a shell portion made of a polycarbonate-based urethane resin so that the ink has excellent discharge stability and storage stability and that images have excellent fastness such as resistance to abrasion and marking with pens. J-PA-2012-92224 discloses the use of a core-shell particle that has a core portion made of an acrylic resin and a shell portion made of a urethane resin so that the ink can be applied to recording media that absorb no ink, such as plastic or metal substrates, and that the ink is highly adhesive, forms good films, and is highly resistant to chemicals.
JP-A-2012-72354 discloses the use of a tri-block copolymer. Although not of a core-shell type, this copolymer imparts excellent storage stability and discharge stability to aqueous inks for ink jet recording and makes images highly resistant to abrasion. JP-A-2006-45304 and JP-A-2004-211089 disclose the use of a crosslinked polymer derived from polyfunctional monomers.
However, the core-shell particle disclosed in JP-A-2002-12802 often causes poor fixation of images because the shell portion has a crosslinked structure. The core-shell particles disclosed in JP-A-2012-25947 and JP-A-2012-92224 improve the fixation of images, but the urethane resin used in their shell portion causes the nozzles of the recording head to be unlikely to recover once clogged. The tri-block copolymer disclosed in JP-A-2012-72354 imparts good discharge stability to ink depending on what monomers the copolymer is composed of, but this copolymer also causes the nozzles of the recording head to be unlikely to recover once clogged. The crosslinked polymers disclosed in JP-A-2006-45304 and JP-A-2004-211089 often cause poor fixation of images.